On Baptism, Against the Donatists
This treatise was written about 400 A.D. Concerning it Aug. in Retract. Book II. c. xviii., says: I have written seven books on Baptism against the Donatists, who strive to defend themselves by the authority of the most blessed bishop and martyr Cyprian; in which I show that nothing is so effectual for the refutation of the Donatists, and for shutting their mouths directly from upholding their schism against the Catholic Church, as the letters and act of Cyprian.